This invention relates to the diagnosis and treatment of AIDS and more specifically to an anti-idiotypic antibody reactive with more than one type of anti-HIV-l antibody. The invention further relates to the use of the anti-idiotypic antibody as a diagnostic and therapeutic agent.
Acquired Immune Deficiency Syndrome, or AIDS, has been described as a modern plague. In the decade since its first description in 1981, it has claimed 120,000 victims in the United States alone. Currently almost 200,000 people are known to be infected with the virus. However, the true impact of the disease has yet to be felt. The virus may remain latent in infected individuals for five or more years before symptoms appear. Many Americans may unknowingly be infected and capable of infecting others who might come into contact with their body fluids. Virtually every person who contracts the virus will develop AIDS and die as a consequence. Thus, if unchecked, the personal, social and economic impact of AIDS will be enormous.
The causative agent of AIDS is Human Immunodeficiency Virus Type 1 (HIV-1). The intact HIV-1 virion is roughly spherical and is approximately 110 nm in diameter. The virion has an outer membrane covered with knobs or spikes made up of glycoprotein, gpl60/120. In addition, there exists a transmembrane protein termed gp41. Inside the virion are two structural proteins: an outer shell composed of the phosphoprotein p17 and an inner nucleoid or central core made up of the phosphoprotein, p24. The viral RNA is present inside the core along with two copies of the reverse transcriptase enzyme, RT or p65, which is necessary for the synthesis of viral DNA from the RNA template. In an infected person, antibodies are made to each of the aforementioned protein components and exist in characteristic concentrations throughout the course of the disease.
AIDS progresses through three stages after HIV-1 infection. The first is an asymptomatic stage during which the host harbors the virus, tests seropositive for HIV-1 antibodies, but does not exhibit any of the symptoms of HIV-related disease. This stage can last for periods as long as five or more years. The second stage, AIDS-Related Complex (ARC), and the final stage, AIDS, are symptomatic and characterized by tumors and a series of opportunistic infections.
Shortly after HIV-1 infection a vigorous humoral response is initiated. This phase is characterized by elevated levels of circulating antibodies. Specific neutralizing antibodies are directed against the various component proteins of HIV-1 and the initial virus is drastically reduced to levels where it is often difficult to isolate. This point marks the beginning of the disease-free phase of HIV infection with its hallmarks of normal T4 counts and high antibody activity against HIV-1 component proteins. However, despite the presence of cellular and humoral immunity in the infected individual, the virus persists and after several years of latency will become active, often mutating to variant forms, and eventually destroying the immune system leading to full-blown AIDS.
In humans, viral infections are typically cleared by two major classes of immune response, a humoral response mediated by B-lymphocytes which produce antibodies and a cell-mediated immune response directed by T-lymphocytes. Individuals who test positive for HIV-1, however, are unable to clear the infection through these two types of immune response. They may remain positive for several years until they succumb to the opportunistic infections characteristic of AIDS. Thus far no case of viral clearance has been reported. The failure of the immune system to eradicate the AIDS virus after infection remains a mystery of HIV infection. It was first explained as a failure of the cell-mediated response due to the destruction of T helper cells (T4) by HIV-1. However, this explanation is difficult to defend since the T4 count remains normal and only a small fraction of T4 cells appears to be infected during the long latent and asymptomatic phases of the disease.
It is now considered likely that abnormalities in the humoral response of B-cells against HIV-1 is at least in part responsible for the ineffectiveness of the immune system associated with HIV-1-related disease. Instead of the normal polyclonal response seen in other infections, the antibody response in HIV-1 infected individuals appears to result in oligoclonal or monoclonal antibody populations. Briault, et al., Clinical and Experimental Immunology 74, 182 (1988).
Traditional methods of diagnosing HIV-1 infection include serological tests to detect the presence of HIV-1 antibodies and polymerase chain reaction for virus detection. However, there are drawbacks to these traditional methods. Although they confirm the absence or presence of HIV-1, they do not indicate the stage of disease progression. Subjects entering the symptomatic stages of disease often fail to recognize the onset of symptoms and delay seeking help. Currently there is no effective treatment for HIV-infection. No effective vaccine is presently available. AZT and other pharmaceutical compounds can temporarily alleviate symptoms in AIDS patients, but have been unable to stimulate the immune system to clear the virus.
Thus, there exists a need for further understanding of the factors which determine the progress of HIV-related disease in order to provide for methods of prevention and treatment of the immune system abnormalities which are characteristic of ARC and AIDS. The present invention satisfies these needs and provides related advantages as well.
The present invention provides compounds specifically reactive with an idiotope common to more than one type of human anti-HIV-1 antibody. In particular, the invention provides an anti-idiotypic antibody which is specifically reactive with more than one type of human anti-HIV antibody, and not specifically reactive to human non-HIV antibodies. A preferred anti-idiotypic antibody of the present invention is the monoclonal antibody designated 1F7, which is specifically reactive against at least three human anti-HIV-1 antibodies of differing specificities, and non-reactive with human non-HIV antibodies. The idiotope recognized by the anti-idiotypic antibody of the present invention, and in particular the idiotope recognized by the 1F7 antibody, is shown to be involved in the clonal suppression of B cells characteristic of HIV infection. The 1F7 antibody is also shown to influence T cell anti-idiotypic regulation. Therefore, the present invention provides a method of regulating the immune response in HIV-infected individuals through treatment with the anti-idiotypic antibody. This is thought to occur through the selective binding of subsets of B and T lymphocytes by the antibody of the present invention. In addition, the presence of the idiotope recognized by the anti-idiotope antibody of the present invention in the sera of HIV-infected individuals is found to correlate with HIV-related pathologies, in particular HIV-related B cell lymphoma. Therefore, the present invention provides a method of diagnosing and monitoring HIV-related pathologies by the reaction of the HIV-infected sera with the anti-idiotypic antibody of the present invention.